Patch "thermal: step_wise: Revert optimization" has been added to the 3.14-stable tree

Patch "thermal: step_wise: Revert optimization" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    thermal: step_wise: Revert optimization

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     thermal-step_wise-revert-optimization.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From jdelvare@suse.de  Wed Jun  3 14:21:51 2015
From: Jean Delvare <jdelvare@suse.de>
Date: Mon, 20 Apr 2015 11:21:13 +0200
Subject: thermal: step_wise: Revert optimization
To: stable <stable@vger.kernel.org>
Cc: Shawn Guo <shawn.guo@linaro.org>, Eduardo Valentin <eduardo.valentin@ti.com>, Zhang Rui <rui.zhang@intel.com>, Borislav Petkov <bpetkov@suse.de>
Message-ID: <1429521673.4305.12.camel@chaos.site>

From: Jean Delvare <jdelvare@suse.de>

Commit 178c2490b99f898efc06d1ad75cadc84f13021a6 ("thermal: step_wise:
cdev only needs update on a new target state") broke driver acerhdf.
That driver abused the step_wise thermal governor until the bang_bang
governor was available, and the optimization broke this usage model.

Kernels v3.12 to v3.18 are affected. In v3.19 the acerhdf driver was
switched to the bang_bang governor and that solved the problem.

For kernels v3.12 to v3.17, the bang_bang governor isn't available
yet so the easiest fix is to revert the optimization.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reported-by: Dieter Jurzitza (https://bugzilla.opensuse.org/show_bug.cgi?id=925961)
Tested-by: Peter Feuerer <peter@piie.net>
Tested-by: Dieter Jurzitza
---
Please consider this patch for stable kernel branches from v3.12 to v3.17.

If anyone cares about v3.18, I think a better fix would be to backport
commit 48c8dd64345ba2a8c41556095c7adacb1c8af7c1 ("acerhdf: Use bang-bang
thermal governor") but it's too big for stable, so it's left to
distributions. So maybe this fix should make it into v3.18 stable as
well - I'll let whoever maintains that branch decide.

 drivers/thermal/step_wise.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/drivers/thermal/step_wise.c
+++ b/drivers/thermal/step_wise.c
@@ -146,9 +146,6 @@ static void thermal_zone_trip_update(str
 		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
 					old_target, (int)instance->target);
 
-		if (old_target == instance->target)
-			continue;
-
 		/* Activate a passive thermal instance */
 		if (old_target == THERMAL_NO_TARGET &&
 			instance->target != THERMAL_NO_TARGET)


Patches currently in stable-queue which might be from jdelvare@suse.de are

queue-3.14/thermal-step_wise-revert-optimization.patch
queue-3.14/hwmon-nct6775-add-missing-sysfs-attribute-initialization.patch